I have recently installed a oil catch can with breathers to decrease my crank case pressure. After installing though, I noticed it doesn't have quite as much pull when accelerating and a little bit into the drive, I noticed my air fuel ratio was much higher (lean I think) than usual, sometimes not even registering on my gauge... Ive tried to do some reading on the subject but not a lot of information particular to my situation. I figured this was the correct section to post even though its on a forced induction vehicle, I thought the subject might be a little broader. Admin, If its in the wrong section please relocate and I apologize in advance. If anyone has any info on this it would be appreciated. Thinking I may need to go get a retune now but wanted to see if anyone else had experienced this.

 

If you removed the PCV valve when installing the catch can then there is no more regulation through that hose and you then have a substantial vacuum leak, which could contribute. That's my theory at least.

 

PCV is ported back into the intake upstream of the map sensor. The only time that would be an issue is with a vehicle that has a MAF sensor in the air box.

 

Pcv has been totally deleted... No valve.... replaced black box with plug and installed the two fittings in the back of the block...

 

The PCV valve prevents the intake from backfiring into the crankcase. If you removed this, you are throwing boost into the crankcase, which will blow out seals in the engine. A catch can needs to be connected to the PCV system's natural air inlet port port on the cylinder head. This line, in a factory setting, cannot be used as designed on a turbocharged car because it will also allow boost to enter the crankcase, causing the same problems because it is the the boosted intake arm to the throttle.

In an ideal situation, the valve cover line will feed into the catch can, and the catch can exhaust line will vent to a breather filter, or the air filter housing before the filter assembly. The latter will help reduce crankcase pressure by allowing the turbocharger to pull a small vacuum (remember, the line is BEFORE the filter, thus the filter restricts full suction) on the crankcase. You could get away with installing this line on the turbocharger suction side after the air filter, but you best be sure the filter element is not a restriction, or else you'll end up with a lot more vacuum in the crankcase than is needed.

In short:

Reinstall the flame arrestor can (black box to you) and the PCV valve as per factory layout. Unless you are boosting at idle, the factory valve is sufficient, do not change its size.
Run a line from your valve cover to the inlet of your catch can.
Run a line from the outlet of you catch can to a breather filter to atmosphere, OR run a line from the outlet to the suction side of you air filter. If you are feeling spicy, you can run it anywhere before the turbocharger.

PS: High boost and larger bore size engines may require additional valve cover vent ports to a catch can to handle the extra blow by caused by using loose pistons/rings. Keep that in mind. If you are unsure, use the paper test on your oil fill cap to see if your crankcase has excessive pressure. The paper should not blow off at idle, and should not blow off much under boost. If it blows the paper off, you need a larger line, or additional vents drilled into your valve cover. You can also use a manometer to get an actual reading on the crankcase.

 

I have 2 an10 fittings coming off the valve cover us the 2 off the back of the block. So basically i need to add a line to the intake side of the turbo and put the black box back on? Im not sure it will go back on with the lines coming off the back. If i take the lines off the block will the crank case pressure be a problem?

 

Your setup is pretty radical, and to a point seems like complete overkill. How much boost are you running anyways? Bore and ring clearance?

All you should have to do, is install the flame arrestor, install the PCV valve, and run a line from that valve to the intake manifold. Don't tee it into your vacuum manifold, the line your using on the manifold is meant for the PCV system, so you may need to drill another fitting on the manifold.

Your two breather hoses with AN fittings should run to the can, and you should have another line coming off to the air filter box before the filter itself. If you have a cone filter, this obviously wont work, so you'll need to either run a line to the turbo intake piping, or simply install a line and leave it tied up and open to the air.

The biggest reason for the PCV valve and arrestor (in addition to safety) is because the crankcase is where the pressure is created, not in the valve cover. Out of boost, air will flow into your breather hoses in the valve cover, and down to the block from the inside. From there, the PCV valve will open, and reduce the pressure in the crankcase. Under boost, the valve will shut, ring leakage and compression loss will create pressure in the crankcase, and will gravitate to the valve cover and your new breather hoses, out to the can. The reason for installing the other line to the air filter box, is to create a small vacuum just like the PCV valve would, so that vacuum, not pressure, is present in the crankcase. The filters on your catch can are more than adequate for a simple release to the outside air, but it could be more ideal, and simpler.

 

I think if you do a compression test you will see you have a messed up piston. My car did the same thing when the ringland broke on #3.

Cylinder #1 had 215 compression, Cylinder #2 had 215, cylinder #3 had "0" and cylinder #4 had 215. I put compressed air in cylinder #3 with all valves closed and all the air was coming out of my catch can.

My AFR's went up just like you describe.

 

Not having a vent to the intake manifold from the crankcase will also cause that, plus your dipstick might unseat under boost. Happens all the time on DSM's.